The invention relates to a radial piston pump of the type, in which an eccentric rotor is adapted to cause the pistons to reciprocatively move within radially extending cylinders.
Known radial piston pumps, such as disclosed in U.S. Pat. Nos. 5,509,347; 5,542,823; and 5,647,729 includes a piston ring surrounded by a casing. A plurality of radially extending cylinders are formed in the piston. Each cylinder receives a piston that is reciprocatively moved in the cylinder by an eccentric rotor. Fluid, such as hydraulic fluid, is drawn into each cylinder through an intake passageway in fluid communication with a fluid reservoir. The fluid is expelled from the cylinder through a radially outer end of the cylinder past a pressure valve into a circumferential passageway formed between the piston ring radial outer surface and an annular member sandwiched between the piston ring and the casing. Compressed fluid in the circumferential passageway flows through a radially directed passageway formed in the piston ring to an axially extending connection for a pressure line
The above described radial piston pump performs adequately. However, servicing the pump requires removing the casing to gain access to the piston ring. If one of the pressure valves requires servicing, the annular member must also be removed. Moreover, if a higher capacity pump is required, a different piston ring having additional cylinders or larger cylinders must be provided which limits the range of pump capacities a pump supplier can provide.